1. Field of the Invention
This invention relates generally to controls for hydraulic directional control valves and more particularly to a hydraulic remote control joystick with an electronic switch to remotely control a solenoid operated pressure build-up valve and provide pressurized flow to actuate a hydraulically operated open-center directional control valve.
2. Description of the Prior Art
Hydraulic directional control valves employing a minimal pressure open center circuit and also being remotely controlled by modulating hydraulic controls require a separate actuator circuit to actuate the spools in the directional control valve. The separate circuit may be powered by either a separate power source, such as a separate pump, or by utilizing the main pump flow. The pressure in the main pump flow is typically in the range of up to 5,000 pounds per square inch when the directional control valve spool is actuated. The separate circuit only requires approximately 100 to 500 pounds per square inch pressure to operate. Therefore, when the main pump flow is utilized, it is advantageous to utilize only a portion of the main pump pressure and flow. This reduction in pressure and flow is accomplished by means of a pressure build-up valve for minimum actuating pressure, a pressure reduction valve to limit the maximum pressure, and a flow control valve to limit the flow of 1-5 gallons per minute when the pressure build-up valve is energized by means of a solenoid.
On a hydraulic remote controlled directional control valve with an open center circuit and using a joystick type of master control, this feature has not been readily adapted for use. It has been necessary to manually actuate the solenoid by means of a separate switch. In an open center circuit, when the spool is in the neutral position, the main pump flow will go through the control valve and back to the tank at a very low pressure. When the spool is shifted to either the right or left, the open center is closed off and the flow is directed to the work ports up to maximum pump pressure. While the design parameters of each open center circuit are different, typically a 3-4 degree movement in the joystick control moves the spool sufficiently to start closing off the open center. Therefore, the signal to the pressure build-up valve in the actuator circuit must be given before the 3 to 4 degree movement of the joystick control. If the signal was delayed beyond the 3-4 degree movement, a hydraulic pressure would be generated beyond the expected starting pressure to the actuator, causing the directional control valve spool to overrun its metering position, and in turn, create a jump pressure condition causing the hydraulic motor to start erratically instead of a smooth operation of the hydraulic motor. Therefore, it has been necessary for the operator to manually energize the solenoid to the pressure build-up valve by separate switch before moving the joystick control.
This invention allows the joystick controller to automatically send a signal via a beam of light located inside the joystick to actuate an electronic relay switch which energizes the solenoid of the pressure build-up valve without the operator actuation of a separate switch.
The control of circuitry by selective illumination and prevention of illumination of a light sensitive element by a light emission device are known. An example of this is a motor control apparatus adapted for use with a motorized vehicle such as a wheel chair. The vehicle includes two drive wheels, each being driven by its own separate motor, a mask, transmittor, and receiver assembly. This assembly can include four light emitting diodes and corresponding, oppositely disposed light receivers. Two of the emitter/receiver pairs are tied to each of the drive wheel motors. One of the pairs effectuates switching to drive the motor in one direction and the other of the pairs is linked to circuitry which causes the motor to be driven in the opposite direction. A mask is innerposed between the emitters and receivers so that light from certain emitters can be selectively unmasked and permitted to illuminate corresponding receivers in order to operate the drive motor as desired.
Another example is a control apparatus which is specifically designed for use in controlling propulsion and brake functions in rapid transit vehicles. The structure includes a fan-shaped mask having arcuate slots formed therein. The fan-shaped mask can be pivoted in a plane generally perpendicular to the direction of light emitted by a number of sources so that, as the mask is pivoted, light will be permitted to pass through various of the slots and illuminate various photo-responsive sensors. Illumination of these sensors actuates control circuits to operate the various propulsion and braking functions.
Still another example of a light operated control device is a structure that inclues a sphere housing and a photocell recessed therein. The sphere is part of a ball joint structure which can be rotated so that a light sensitive side of the photocell can be illuminated by various light emission devices positioned about the sphere. The photocell is connected to control circuitry which is used to effectuate various functions.
In another control device, the functions are not controlled by allowing illumination of a light sensitive photocell and selective interruption of the illumination. Rather, the illumination is constant, with the function being controlled by the color of the light which is received by the photo detector array. The color of light which is received is controlled by selective rotation of a knob at the end of a control stick. Rotation of the knob causes the color of the light to be varied by interposing a mirror coated with a different colored filter material in the path of the light beam.
To date, there are no known control structures for remotely controlling hydraulic directional control valves that also accomplish the function of remotely controlling a solenoid in a separate actuator circuit by means of an electronic relay switch controlled by a beam of radiant energy incorporated within the joystick controller.
The present invention addresses the problems associated with the prior art devices which require an operator to operate a separate switch from the joystick controller to operate the solenoid on a separate actuator circuit. The present invention provides a ready means for effectuating both the control of a hydraulic directional control valve and energizing a solenoid with one control handle.